1. Field of the Invention
This invention relates to an engine lubricating system, and more particularly to a system for controlling the amount of lubricant to be supplied to the combustion chamber in a Wankel engine, a two-cycle engine or the like.
2. Description of the Prior Art
As disclosed in Japanese Unexamined Utility Model Publication No. 60(1985)-3201, for instance, in a Wankel engine and the like, a measured amount of lubricating oil is supplied to the combustion chamber by a metering oil pump to lubricate the moving parts in the housing separately from the main lubricating system. In such a lubricating system, the amount of oil to be supplied to the combustion chamber is controlled by the metering oil pump. That is, the metering oil pump generally discharges lubricating oil in synchronization with engine revolution by way of a plunger driven by the engine output shaft, and the stroke of the plunger is controlled by a cam provided on a control pin which is rotated in response to the throttle valve, thereby controlling the amount of lubricating oil to be discharged from the metering oil pump per unit engine revolution.
In the conventional system, the oil discharge rate of the metering oil pump (the amount of lubricating oil to be discharged from the metering oil pump per unit engine revolution) changes solely according to the engine load (the throttle opening) irrespective of the engine speed. However, the lubricating oil requirement per unit engine revolution changes with the engine speed. That is, since the temperature of the moving parts rises as the engine speed increases, the lubricating oil requirement increases with increase in the engine speed. Accordingly, if the oil discharge rate of the oil pump is set to meet the lubricating oil requirement at a low engine speed, lubricating oil will be insufficient during a high speed operation of the engine, and on the other hand, if the oil discharge rate is set to meet the lubricating oil requirement at a high engine speed, lubricating oil will be excessive during a low speed operation of the engine.